The present invention relates to plungers operable for lifting fluids in well casings or other tubulars from subterranean formations.
Various types of casing plungers have been used heretofore for lifting and recovering or removing oil, water, or other fluids from well casings. In some wells, due to relatively low formation pressures and/or other formation conditions, liquids tend to accumulate at some level in the well casing rather than flowing naturally out of the well. Casing plungers offer potential benefits over conventional pumps, submersible pumps, and other power operated devices for recovering or removing such fluids.
One type of casing plunger currently available comprises: an elongate housing assembly; one or more external sealing devices which project from the housing and sealingly contact the well casing as the plunger travels up and down in the well; a flow passage extending through the assembly and having openings below and above the external seal(s); and a valve assembly for opening and closing the flow passage.
In a typical production cycle wherein a casing plunger is used to recover or remove accumulated liquids from a well casing, the plunger is dropped from the upper end of the well casing with the plunger valve in open position. The fluid accumulated in the casing will thus flow internally through the housing flow passage so that the plunger will fall to a desired downhole position. The desired downhole position can be set, for example, by placing a stop structure in the well casing.
Upon reaching the desired downhole position, the plunger valve typically will close so that the plunger will effectively seal the casing. As formation gas builds beneath the sealed plunger, the pressure beneath the plunger increases. Eventually, the pressure beneath the plunger will increase to the point that the plunger will begin to rise in the casing, thus lifting the column of fluid on top of the plunger toward the surface and into an overhead product line. Upon reaching the top of the well, the plunger valve opens so that the pressure beneath the plunger is released and the plunger is ready for another production cycle.
Unfortunately, the casing plunger devices heretofore known in the art have had significant shortcomings. As indicated, for example, in U.S. Pat. No. 4,923,372, external elastomeric-type sealing elements are particularly desirable for sealing the gap between the plunger housing and the interior wall of the well casing. However, the continuous contact of the elastomeric seal with the casing wall as the plunger travels up and down in the well casing can cause the elastomeric seals to wear very rapidly, thus requiring frequent repair and replacement and sometimes resulting in valve failure. Alternatively, other prior art devices employ sealing elements which are mechanically engaged with the well casing as the plunger moves upward within the well but are supposed to be mechanically disengaged from the casing wall as the plunger falls downward. In practice, however, these devices typically bounce against the interior wall of the casing as they fall through the well, thus causing significant wear and damage to the exterior components of the plunger.
The present invention provides a plunger for well casings and other tubulars which satisfies the needs and alleviates the problems discussed above. In one aspect, the inventive plunger comprises: a body having a flow passage, the flow passage having at least one inlet port and at least one outlet port positioned above the inlet port; a valve positioned in the flow passage (preferably in the upper portion of the tool) between the outlet port and the inlet port; a flexible sealing member retained around the body; and an actuator engaging the flexible sealing member such that, when the valve is closed, the actuator will urge the flexible sealing against the interior wall of the well casing.
In another aspect, the inventive plunger comprises: an elongate body having a flow passage, the flow passage having at least one inlet port and at least one outlet port positioned above the inlet port; a valve positioned in the flow passage between the outlet port and the inlet port; a first flexible sealing member positioned around the body below the outlet port; an actuator operably linked to the flexible sealing member such that, when the valve is closed, the actuator will cause the flexible sealing member to contact and seal against the well casing; a second flexible sealing member positioned around the body and providing an outwardly expandable sealed chamber around the body; and at least one flow port, positioned below the valve, providing fluid communication between the flow passage and the sealed chamber. The second flexible sealing member is outwardly expandable by increasing pressure in the sealed chamber such that the second flexible member will contact and seal against the well casing.
Further objects, features, and advantages of the present invention will be apparent to those skilled in the art upon examining the accompanying drawings and upon reading the following description of the preferred embodiments.